class PrivateStream

class PrivateStream extends LocalStream {
    
    /**
     * {@inheritdoc}
     */
    public static function getType() {
        return StreamWrapperInterface::LOCAL_NORMAL;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getName() {
        return t('Private files');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDescription() {
        return t('Private local files served by Drupal.');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDirectoryPath() {
        return static::basePath();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getExternalUrl() {
        $path = str_replace('\\', '/', $this->getTarget());
        return Url::fromRoute('system.private_file_download', [
            'filepath' => $path,
        ], [
            'absolute' => TRUE,
            'path_processing' => FALSE,
        ])->toString();
    }
    
    /**
     * Returns the base path for private://.
     *
     * Note that this static method is used by \Drupal\system\Form\FileSystemForm
     * so you should alter that form or substitute a different form if you change
     * the class providing the stream_wrapper.private service.
     *
     * @return string|null
     *   The base path for private://. NULL means the private directory is not
     *   set.
     */
    public static function basePath() {
        return Settings::get('file_private_path');
    }

}